Control for systems using either heating or cooling medium



9 R. C 8 w 5 mi@ N w i@ Q n N v r L. ,f S E c gwmmg u Y m i a .m w w, W QN QN www2 NY @mmm sum mm2 RTO uw BSC u .HRA D Od @GM LT 0A m m N O C Dec. 26, 1950 Patented Dec. 26, A1950 CONTROL FOR SYSTEMS USING EIVTHER HEATING OR COOLING MEDIUM Charles D. Branson, Knoxville, Tenn., assignor to RobertshawFulton Controls Company, Knox-` ville, Tenn., a corporation of Delaware Y Application August, 2, 194s, serial No. 41,963

i 11 Claims. t l

,'Ihis invention relates to temperature responsive controls and more particularly to temperature. responsive controls for use in systems comprising a central plant for circulating either a heating or a cooling medium and automatically operable to properly condition the system when changing over from a heating to a cooling medium or vice versa..

Where a central plant is used for supplying air conditioning medium to a plurality of users, whether they be different tenants in the same building or occupants of a plurality of buildings, having regardto the fact that diierent users will consume different quantities of air conditioning medium to suit their particular requirements, it has been proposed to determine the payment to be made `by each user by metering the quantity of medium used by him over a predetermined period of `time and, knowing the differential in temperature between the iniiowing and outiiow- 13 ing medium, the charge made may be directly correlated with the quantity of heat involved in each users individual consumption. When a central plant of this character is used both for supplying heating medium in cold whether and a cooling medium in hot weather it is desirable that the system shall include provisions whereby it is automatically conditioned from the character ofthe medium being circulated so as to `ing the direction of flow of said medium with respect to the elements used in the system.

, Another object of this invention is to provide a system of the type last characterized with means whereby there will be a predetermined heat differential between the medium being dependent upon the temperature of the medium `for predetermining the direction of iiow of said medium with respect to said regulator.

Another object of 4this invention is to provide a system of the type characterized with automatic mechanism for reversing the direction of flow through the consumers equipment as the medium delivered is changed from a heating medium to a cooling medium or vice versa.

f Another object of this invention is to provide a system of the type last characterized which includes automatic mechanism for predetermining the differential in temperature between the medium delivered and the medium returned whether such medium be a heating medium or a cooling medium.

Another object of this invention is to provide a system of the type rst characterized wherein all of the regulators used may be of simple construction, easily installed and accurate in operation.

Another object of this invention is to provide a systemv of the type characterized which is sim ple in arrangement and easily adjustable, so that the temperature differential between the me dium delivered and the medium returned may be easily predetermined and thereafter known with certainty whereby, when combined with a suitable metering device for predetermining the quantity of medium circulated through the individual users equipment, a, satisfactory basis vfor lixing charges based on number of heat units involved may be provided.

Other objects will appear as the description of the invention proceeds.

The invention is capable of receiving a variety of mechanical expressions only one of which has .been illustrated schematically on the accompanying drawing. It is therefore to be expressly understood that the drawing is for purposes of `illustration only and is not tobe construed as a deiinitionof the limits of the invention, reference being had `to the appended claims for that purpose.

Referring in detail to the accompanying drawing, there is illustrated, for the most part diagrammatically, but with certain parts broken away to facilitate understanding, a system of `the character hereinbefore referred to, the automatic control being shown to a larger scale than the remainder of the system.

In the system diagrammatically illustrated a plurality of heat exchange units ID are shown as cross connected between conduits Il` and l2, typifying the air conditioning equipment for heating or cooling of a single user. However, `as will be apparent to those skilled in the art the units I0 m-ay also typify the equipment of separate tenants in a single building or equipmn ill a .plurality AQf separate buildings. A c entral plant (not shown) for supplying either heating or cooling medium, depending upon the season of the year, delivers the medium to be circulated through the units IIJ to a conduit i4 in which may be disposed any suitable meter I5. If said meter I5 is to measure the quantity of medium consumed by .an individual user as will be assumed in the `further explanation of the present invention, then the automatic crossover and regulator to be described will be individual to each user. However, as will be apparent, the meter may be associated with each .of .the units IIJ and the automatic crossover and regulator to be described may control the vsupply of medium to all of said units. In the ensuing description, however, it will be assumed that the vautomatic crossover and regulator to be described are individual to each consumer, and therefore vthe meter IIlis the meter by which is measured the quantity of heating or cooling medium delivered to such consumer.

From the meter I5 :extends a supply conduit .l5 of any suitable size, length and character which communicates with a housing I1 through which the circulating medium is caused to flow. Housing I1 has any suitable connection .I3 leading from its interior to the interior of a housing I9 from which extends a conduit 2|] leading to the interior of the housing 21 of 'a thermostatically controlled valve mechanism to be described. Conduit 22 connects the interior -of .housing 2l with .the interior -of the housing 23 'of a. second .thermostatically .controlled valve mechanism to be described, and in communication with the interior of said housing 23 `are two conduits 24 and 25 of any suitable length, size and character that communicate with .the interior of housings '25 and 21, respectively. Housings 2S zand 21. are in communication with conduits 23 and 2i!v which are respectively in communication with the :aforesaid I communication with the vinteri-or oi housing 32 is u a return conduit 33 of any suitable length, size and character for returning the circulating medium to the central plant.

The thermostatically controlled valve mechanism' whose housing is indicated at 2Il is for the purpose of maintaining a predetermined temperature differential between the medium delivered to the units I0 and the medium returned from said units. Any suitable thermostatically controlled valve mechanism for maintaining a predetermined drop in temperature between two points in a system may be used at this point. The construction illustrated diagrammatically is or the type disclosed in the patent to Reeder, No. 2,211,612, of August 13, 1940 and, as shown in said' patent, is preferably made adjustable so that the temperature drop between the selected points may be closely predetermined. As illustrated; 'housing 2l is provided with an interior partition 35 in which is a valve port 3S. Cooperating with said Aport 33is a valve member 31 connected to a stem 38 that is operatively associated with the movable end walls of two expans'ible and collapsible chambers. As here shown,I a. .rigid 4 cup-shaped exterior wall 39 is mounted on or is an extension of the housing member 34 and has hermetically secured therein in any suitable Way an expansible and collapsible corrugated tubular wall or bellows 40 forming an expansible and collapsible chamber 4I between said bellows and said :cup-shaped wall. Disposed interiorly of said bellows 40 is a second expansible and collapsible corrugated'tubular wall or bellows 42 which is hermetically secured in the cup-shaped wall in any suitable way `and in conjunction with said bellows 40 forms an expansible and collapsible chamber 43 between the two. The movable end wall of bellows l42 is operatively connected to the stem 38 foroperating the valve member 31 under the Icontrol of the combined relative expansions and contractions of the two chambers 4I and 43.

Connected to the cup-shaped member 39 in any .suitable way and in communication with the chamber 4I is a conduit v44 of any suitable length, size and construction, preferably a capillary tube. which leads to -a temperature responsive element in the form fof Va bulb mounted in any 'suitable way the housing 21 and preferably extending into the conduit 29. Also mounted on 'saidcupshaped member 39 in any suitable Way :and :in communication with the expansbl'e and collapsible chamber 43 is a conduit 46 :of .any suitable length, size and construction, preferably a -capil'lary tube, extending to a temperature responsive element in the form of a bulb 41 mounted in any suitable way in thefhousing 26 and preferably extending into the conduit 28. The bulb 45 with its expansible and collapsible chamber 4I in communication through the conduit 44 is ycharged with any suitable thermosensitive huid so as to effect .expansion .and contractionof the chamber 4I in response to variations oftemperature at the bulb 45. Similarly, the bulb -41 together with its expansible and collapsible `chamber 43 in commun'ication through the conduit 46 is* charged with a suitable thermosensitive iiuid-so as to effect expansion and contraction of the chamber 43 in response to variations of temperature at the bulb 41. The construction is such that the composite ei'ect of the expansions and contractions of the two chambers 4I and 43 are transmitted through the stem 38 to the valve member 31 so as to con 'trol the flow of medium through the port 36 to the end that a definite predetermined drop Aof temperature may exist between bulbs 45 and 41 as fully explained in the aforesaid patent to Reeder. A-s 'before pointed out, the housing member 34 for this differential thermostatically controlled valve mechanism preferably includes provisions for'adjusting the temperature differential to be maintained between the bulbs 45 and 41 as fully disclosed in said patent to Reeder. While a differential valve mechanism of the type disclosed in said Reeder patent is illustrated herein, it is to be expressly understood that any other suitable diiierential thermostatically controlled valve mechanism may be disposed at 2| so as to maintain a predetermined temperature diierence4 between the housings 26 and 21 or their associated conduits 28 and 29. y

Housing 2.3 has associated therewith any suitabie thermostatically controlled valve mechanism `for determining whether the .cir-culat'on .of medium leaving said housing shall be through the conduit 24 or the conduit'. As illustrated, the thermostatically controlled valve mechanism is of the type disclosed in the patent tol Giesler, No. 1,885,711, dated November l, 1932. The housing 281'is Shown as provided interiorly with a pair of partitions 50 and 5I in which are provided suitable valve ports 52 and 53. The chamber 54 between said partitions is in communication with the conduit 22, while the chambers 55 and 55 at the outer sides of said partitions are respectively in communication with the conduits 24 and 25. Disposed in said chamber 54 is a valve member 51 of any suitable character connected to a stem 58 that is operatively associated with movable end wall 59 of an expansible and collapsible chamber 5l) formed between a cup-shaped Wall 6I, mounted on the housing 23 in any suitable way, and an expansible and collapsible corrugated tubular wall or bellows 62 hermetically connected in any suitable way to the interior of said cupshaped wall. In communication with said chamber 60 is a conduit 63 of any suitable length, size and construction, preferably a capillary tube, leading to a temperature responsive element in the form of a bulb 64 mounted in any suitable way in the housing I9 and preferably extending into theconduit 2U as shown. Bulb 64 together with its chamber 60 in communication through the conduit 63 is charged with any suitable thermosensitive lluid so that upon expansion or contraction of the chamber 60 in response to a Sullicient change of temperature at bulb 64 the valve member 53 will be moved from one of its positions to the other, closing the port 53 or the port 52,

respectively, to compel all of the medium circulating through vthe housing 23 to leave by the conduit 24 or by the conduit' 25, respectively.

The housing 32 is also provided with any suitable thermostatically controlled valve mechanism for predetermining whether the flow of circulatz able valve member 13 connected to a valve stem 14 operatively associated with the movable end Ywall 15 of an expansble and collapsible chamber .16 formed between a cup-shaped housing 11 mounted on the housing 32 in any suitable way .and an inner expansible and collapsible corru- ,gated tubular wall or bellows 18 hermetlcally connected to said cup-shaped wall 11 in any suitable way. Chamber 16 is in communication with a -conduit 19 of any suitable length, size and construction, preferably a capillary tube, which leads to a temperature responsive element in the form of a bulb 85 mounted in any suitable way in the vhousing I1 and` preferably extending into the conduit I6. Bulb 80 together with its chamber 15 in ,communication through the conduit 1S is charged with any suitable thermosensitive fluid so that upon a suicient change of temperature at the l,bulb 80 chamber 16 will be expanded or contracted to move valve member 13 from one of its positions vto the other, closing the port 69 or the port 58,

respectively, so as to place conduit or conduit 3|, respectively, in communication with return .conduit 33.

Each of the -thermostatically controlled valve mechanisms associated with housings 23 and 32 4are preferably made adjustable as fully disclosed .in the aforesaid patent to Giesler. While the 6. thermostatically controlled valve mechanisms associated with the housings 23 and 32 have been illustrated as of the type disclosed in said Giesler patent it is to be expressly understood that any other suitable thermostatically ,controlled valve mechanism may be used for predetermining the iiow through the ports 52 or 53, on the one hand, and the ports 68 and 69, on the other hand., vpursuant to changes of temperature at the bulbs 64 and 80, respectively, such as would occur upon changing from a heating to a cooling medium or vice versa.

Assuming that thedifferential valve mechanism associated with the housing 2| is so constructed that the temperature differential to be main'- tained by the expansion and contraction of the chambers 4I and 43 is such that chamber' 4| determines the lower temperature, it is apparent that the circulating medium of lower temperature must iiow in heat interchanging relationship with the bulb while the medium of higher temperature must flow in heat interchanging relationship with the bulb 41. In the case of a heating medium the lower temperature is on the return side of the heat exchanger units, while in the case of a cooling medium the lower temperature is at the delivery side of the heat exchanger units. Therefore, in order that the medium at the lower temperature shall always flow into heat interchanging relationship with the bulb 45 while the medium of higher temperature shall always flow into heat interchanging relationship with the bulb 41 it is necessary that the ilow of 'circulating medium be changed or crossed over whenever a switch is made from heating medium to cooling medium or vice versa. The control as heretofore described effects this cross over automatically.

Assume that heating medium is received by conduit I4 from the central unit. After it flows through the meter I5 it flows through the conduit IB, housing I1, connection I8, housing I9 and conduit 20 as indicated by the dotted arrows'. Contact of the heating medium with the bulb 64 effects expansion of its communicating chamber E0, moving the valve member 51 to close the port 53. Therefore, the heating medium from conduit 2U, after flowing through housing 2| and conduit 22, flows from the chamber 54 through port 52 into chamber 55 and thence through conduit 24 and housing 25. Whether the medium shall leave housing 26 through conduit 28 or through conduit 3U depends upon the position of valve member 13. Contact of the heating medium with bulb 80 effects an expansion of the chamber 15, causing valve member 13 to close the port 69 and thereby prevent flow of said medium through the conduit 30. Hence the heating medium flows from conduit 28 to the conduit II, through the units II), and out through conduit I 2 and conduit 29. From conduit 29 the heating medium flows through conduit 3| into chamber 12 and thence through the now open port 68 to return conduit 33.

Assume now that a cooling medium is delivered by the central plant to conduit |4. After passing through the meter I5 the cooling medium flows through conduit I6, housing I1, connection I8 and housing I9 into conduit 20. Contact of said medium with bulb 64 causes a contraction of chamber moving valve member 53 to close port 52 and open port 53. Therefore, the cooling medium, as shown by the solidarrows, after owing through housing 2| andiconduit 22 will enter chamber 54 and thence ilowfthrough port 53, conduit 25 and housing 21..;Whether. the cooling l l'iievzlium;v shall flow-fromrhousine 21;tofconduits` or'fconduit 31 again depends on the position of Contact of the cooling..

the;y valve member; 13; medium with the-bulbrlll)` eects contraction of. chamber 16:` toY move valve member I3 to close port; 6,8' and thereby prevent` flow` of the medium through` conduit 3|; flows through the conduit 29'to conduit I 2: and thenceV through the unitsfl in the oppositedirectionv from thevflowwhenheating medium is beingY circulated. From unitsv l)V the cooling medium returns through conduits ll and 28, housing-,2B and1conduita3l,and asport t9Y isnow open the mediumu flows into chamber I-and out through. return conduit-33.

In either event, the medium in heat interchangefrelationship with the; bulb 45 is at alower temperaturev than the medium in heatinterchanging relationshipwith the bulb 41. Therefore; underthecomposite action of the expansible and; collapsible chambers 4I- and 43 as determinedgby thetemperature variations at bulbs 45 and' 4.1,` valve'member- 3l is properly positioned to regulate'the flow-of medium through the port 3,6"for producing the predetermined temperature drop:y betweenybulbs 41y and 45' as set by the adjustment ofthe differential valve at 2 l.

lThe:` temperature drop between the medium being supplied and the medium being returned to thecentral plantbeing thus predetermined by the; setting:y of the differential valve at 2| and the quantity of medium flowing through units l-ilbeingdeterminable from the meter,` i5, itispossible to exactly com-pute the number of heat units? delivered'A or absorbedA by the consumers units; I 0 and thereby base his; charges accurately on his consumption,

Each of theunitsv Ill may have its own thermostatic control so asstomaintain the-desired temperature in-each ofthe spaces beingfconditioned byl a unit l0. This is: diagrammatically illustrated` inl the drawing wherein each ofrthe units I0 isgshown as provided with a thermostatically controlled valvemechanism: 8| actuated.. byI a thermostat 82- of any suitable character subjected to the temperaturefof the ambient: Any suitablethermostatically controlled valve mechanismmaybe-used for so regulating-theunits il! ir'idividually.

It-.zwfil'l therefore beiperceived that theA present invention` provides: a simple, certainand automatic mechanism whereby -a l predeterminedtemfperature-differencez may be maintained between the;incoming` and outgoing-circulating. medium Whether-thatmedium isi ay heating mediumor. a cooling:v` medium, and proper circulation o1v the mediumiwith respectY to the ytemperaturey responsive elements of the control is automatically effected. by valve mechanism responsive to the temperature: of. theamedi'um being circulated and responding automatically thereto to cause the `direction ofy circulation to'A conform with' the requirements of the differential valve mechanism which'f maintains the predetermined temperature Idifference between inflowing: andl outlowingl mediurni` All oftheelements composing the-control 'maybeoi standard construction, and the; control can be: easily. installed', it occupies littleY space, and iti yetl assures: accurate measurementof the quantity andi temperature dropv o-fthemedium beingcirculated whether itlbe a: heating medium orV aV cooling: medium.. i

. While-.the-embodimenti-of the-invention illustrated on: thea drawing has; been described: with cuinsderablei parti'cularit'y,` iti-is. to be.A expressly Hence-the cooling medium'y Cil understood. that., mel intention is not` melted theretoV asV the; same is capable4 of receiving,- a variety of` mechanical expressionaas wilLnow-.be

apparent .tothoseskilled in theart, while changes` may be madeindetails without departing-from1 the spirit of thisinvention. Theautomatic control provided by the presentinvention may be situated: in, any convenient ,location with. respect',

to` the units; I0, andV the thermostatically con-v trolled)I valve mechanisms employed may be vari-fA ously located withlrespect to the supplyand returnconduits andjbe of any suitable construction to eiect .operations in conformityl with' the.: fore goingexplanation. The meter, lcouldobviously be installed in communication withk the return conduit, and'other'changes in details of construe,.- tion, relative arrangement, etcz, willreadilyzsugf gest;themse1ves to those skilled in the art. Refer.- ence is thereforeto behad to the appendedclaims forazde'nitionof the invention.

What: is. claimed.- is:

1. InA ac system for circulatingeither-afheatlng medium or acooling mediumthrough heat,-einl changers, in combination with a supply-conduity andaareturnzconduit for the circulating medium and a pairof conduits through which the medium Hows to and from the heatexchangers; thermostatically controlled valvey mechanism for: maintaining a predetermined.temperature diier.- ence'v between the medium. flowing.- through the supply and return conduits andincluding apair of temperature responsive elements respectively subjected tothe temperature of the medium lowing-through` ther-conduits of'said pair, cross over connections connecting each of-'said-supply and return conduits tobo-thof said'pair of-conduits; and thermostatically controlled val-vemechanism subjected to the temperature of the medium iiowingthrough said'supply conduit and cooperating Withsaid cross over connections'for-predeterminingfthed-irectionof flow of said.` medium through said pair of conduits depending upon whether-it is a-hcating medium or a cooling medium;

' 2. In asystem for circulating eithera heating medium or a cooling medium through heat ex*- changers, in combination with asupply conduit and areturnconduit for the circulating medium and a pair of conduits through which the medium flows toY andy from the heat' exchangers, thermostatically controlledvalve mechanism for maintaining a predetermined*temperaturesdifferto be subjected to the hotter medium owing througlrsaidv pair offco'nduits whether the medium be a heating medium'or a cooling medium.

3; In a system` forcirculating eitheraheating mediuml or a cooling medium through heat eX'- changers, in combination with a supplyconduit and a` return conduit for the 'circulating medium and-apair'ofconduits through-which the'lmedi'um .ow's to and from the? heat exchangers-,- thermostatically controlled valve''mechanisrn for-'maintaining a predetermined temperature dilerence between the medium flowing through the supply and return conduits and including a pair of temperature responsive elements respectively subjected to the temperature of the medium iiowing through the conduits of said pair, cross over connections connecting each of said supply and return conduits to both of said pair of conduits, and a pair of thermostatically operated valve mechanisms including temperature responsive elements subj ected to the medium flowing through said supply conduit for controlling said cross over connections and reversing the direction of circulation through said pair of conduits upon change from heating medium to cooling medium or vice versa.

4. ln a system for circulating either a heating medium or a cooling medium through heat exchangers, in combination with a supply conduit and a return conduit ior the circulating medium and a pair of conduits through which the medium hows to and trom the heat exchangers. thermostatically controlled valve mechanism i'or maintaining a predetermined temperature dlilerence between the medium flowing through the supply and return conduits and including a pair of temperature responsive elements respectively subJected to the temperature ci' the medium nowing through the conduits of said pair, cross over connections connecting each of said supply and return conduits to both of said pair of conduits, a valve mechanism including a housing in communication with said supply conduit and having a pair oi' outlets respectively communicating with said cross over connections and a pair or ports for controlling said outlets, a valve member in said housing ior controlling said pair oi' ports, a thermostat having a temperature responsive element subjected to the medium flowing through said supply conduit and operatively connected to said valve member, a second valve mechanism including a housing in communication with said return conduit and having a pair of inlets respectively communicating with said cross over connections and a pair of ports for controlling said inlets, a valve member in said housing for controlling said pair of ports, and a thermostat having a temperature responsive element subjected to the medium owing through said supply conduit and operatively connected to said last named valve member.

5. In a system for circulating either a heating medium or a cooling medium through heat exchangers, in combination with a supply conduit and a rettun conduit for the circulating medium and a pair of conduits through which the medium ilows to and from the heat exchangers, the combination ci' a thermostatlc diiierentially controlled valve mechanism having a housing in communication with the supply conduit and including a pair of temperature responsive elements respectively subjected to the temperatures ofthe medium owing through said pair or conduits, a pair of thermostatically controlled valve mechanisms having housings in communication with said iirst named housing and with said return conduit respectively and including temperature responsive elements subjected to the medium ilowing to said iirst named housing, and cross connections between said pair of housings and said pair of conduits controlled by said pair of thermostatically controlled valve mechanisms to cause circulation oi said medium through said cross connections in such a direction that whether heating or cooling medium is being circulated one of the temperature responsive elements of said dilerential valve mechanism is always subjected to the cooler medium and the other of said temperature responsive elements is always subjected to the hotter medium owing through said pair of conduits.

6. In a system for circulating either a heating medium or a cooling medium through heat exchangers, in combination with a supply conduit and a return conduit for the circulating medium and a pair of conduits through which the medium nov/s to and from the heat exchangers, means for maintaining a predetermined drop in temperature in the medium between said pair of conduits whether a heating medium or a cooling Vmedium is being lcirculated, said means comprising a valve housing in communication twith said supply conduit and thermostatic differentially controlled means for operating said valve mechanism including a pair of temperature responsive elements respectively subjected to the temperature of the medium owing through said pair of conduits, and means whereby the hotter medium and the cooler medium in said pair of conduits always ilow in heat interchanging relationship with the same temperature responsive` elements respectively Whether a heating medium or a coo-ling medium is being circulated, said last named means comprising a valve mechanism having a housing in communication with said supply conduit and a pair of outlets communicating respectively with said pair of conduits, a valve mechanism having a housing in communication with said return c-onduit and having a p-air of inlets respectively communicating with said pair of conduits, and two thermostats operatively connected to said last two named valve mechanism respectively and each having a temperature responsive element subjected to the medium owing through said supply conduit.

'7. In a system for circulating either a heating medium or a cooling medium through heat eX- changers, in combination with a supply conduit and a return conduit for the circulating medium and a pair of conduits through which the medium ilows to and from the heat exchangers, means for maintaining a predetermined drop in temperature in the medium between said pair of conduits whether a heating medium or a cooling medium is being circulated, said means comprising a valve housing in communication with said supply conduit and thermostatic differentially controlled means for operating said valve mechanism including a pair of temperature responsive elements respectively subjected tc the temperature of the medium flowing through said pair of conduits, and means for reversing the direction of flow of the medium through said pair or conduits depending upon whether a heating medium or a cooling medium is being circulated, said last named means comprising a pair of valve mechanisms having h-ousings respectively in communication with said supply and return conduits and each in communication with both of said first named pair of conduits and including a Valve member cooperating with a pair of ports for determining through rwhich ofthe conduits in communication with said nrst named pair of conduits the circulating medium shall flow, and a pair oi thermostats operatively connected to said valve members respectively and each including a temperature responsive element subjected to the medium flowing through said supply conduit.

8. in a system, fer circulating either ai heating inediurn or a ooo-,line rhodium through heat exoh "rigors, in kooihh mation with a ,supply conduit -ano return conduit for ,the circulating medium anda pair of oohtiuits through which themedium hows to .and from'the heat eaohan'eers., means for maintaining a predeterminedlrop in temperature in ,the medium between said Vpair of conduits Whether a heating medium or a cooling medium is `being circulated, said means comprising a Valve housing in communication with said supply conduit and thermostatic differentially controlled vmeansfffolr operating said valve mechanism includngfa .pair :of temperature responsive elements respectively subjected to the temperature of the vvnleliurn flowing through said pair of conduits, and'rneans forreversing the direction of ilow of the vrneoliuni .through said pair of conduits depend- 'iing upon Whether a lheating medium or a cooling mediurnis heine circulated, a valve housing in cornmunication'with both lof said pair of conduits and in continui.lisation with Said ,supply oohiiut a valve housing in communication with 'both of said pair of conduits and with said return ,Conduit apair of valve mechanisms in said last vnamed vl; u sings respectively for selectively predeter- V, ing through which outlet and which inlet said medium shall flow, `rand a pair of thermostats operatively connected to said valve mechanisms respectively and eaoh having, temperature respon'sive element subjected to medium flowing through solo sourir Conduit '9. In a system for circulating a heating medium ora .oooiiiienieoiuhi' through heat exchangers in 4combination with a supply conduit and areturn conduit Afor'the circulating medium and a pair of conduits through which the medium iioWs to and fromy the heat exchangers, a valve housing in communication with said supply conduit and connected to both o f said pair of conduits, a second valvehousing in communication with said return conduit and connected to looth of said pair of conduits, valve mechanism in eaoh of said housings and operalole to reverse the direction of flow through said nair of 'Conduite .by Seieotine the connections through Which the medium shall flow, a the,rrhostat operatively connected to each of said yalve mechanisms andhaving a temperature re- Sill@ @lement Subjecfd tothe .medium flo-Wing thr eh salti Supply Conduit, .and thermostatieally controlled valve ineoiiohisiu in one. o f .said oonduits allo haring ineens. responsive to the ternoerature of the. hoeoiuihfiowing through both of said. pair oi conduits for maintaining a Predeterr'hiheo temperature. drop'therebetween 1.0,- In a. system for measuring the units of heat involved in air conditioning systems in which either la heating rheoiurn or a cooling medium is to circulatethrough heat'exchangers, in Ycomloination with a meter for measuring the quantity of medium being circulated, supply and return conduits one of Which is in communication with said meter,l and a pair of conduits through Which the medium may ow to and from the heat exv,ciiitsjtor con. 'ng .the nov of roeliiuin therethroush, themes/tatie `means operatively oonneeted to said valve meohanisinand vhal/iris temperature responsive elements respectively @subjected to the medium flowing :through said pair of manoirs, saidtnermostancauy operated ,valve mechanism l loredeterminineV the oiiiererioe in ionifileiohure in .the .medium respectively iiowing through .saisi iol-y anti Vreturn conduits., and

changers. a vail' @mechanism .in one of saiti .ooh-V foreahs for reviorsiusthe ,oireetionof -fiow through saisi pair of conduits rwhen shane-ing trom a heatins medium to La cooling medium or-Viee versa, said last named ineens inoiuoling pair of Valve housings respectively in communication with said supply and return .conduits .and each having a lpair ,of connections in communication with-fboth `of said p air of conduits, valve mechanism virrxteach .of said valve housings for .predetermining through `whichef said .pairof connections .the medium may flow :and .thermostats operatively connectednto each .of 4said last named ,valve mechanisms and responsive to the temperature .of the medium ilowing through said .supply conduit.

In a system for measuring .the units of heat involved in ,air conditioning systems which Y Y Y. Y at valve member 'for predetermining the rate of now through Soiii Conduite, a Pair of thermostais operatively oonfneoteo to. said Valve 'member and having temperature responsive elements resoeotivel'y'subjected to Ythe medium ovving through said "Lair of conduits, ano means .for reversing ltliedi] tin of flow through' Said lpair of conduits 'on o. .ange from a heating medium Vto a cooling rnedllm Ol 'vice versity v.Sitid last named means including a pair 'of thermostatically controlled 'valve members .for Controlling Whioh of said pair of ooniiuiis Vshall be in Communication with said suppl;7 conduit While connecting 1he other of said Apair of conduits to said return conduit, 'said last named thermostats including temperature responsive elementssubjected'to the medium flowing through said *supplyA conduit.

CHARLES D. BRANSON.

REFERENCES CITED The, following references are of record in the le of this `patent: i

Number v'Name Date V2,182,691 Crago i" Dee. 5, 1939 353,889 Giesler July 18, V1944 

